Straight Pipes

You are exactly right, exhaust gas scavenging is not factor. The turbocharger creates enough back pressure that anything coming out of the housing is spent.

Where the horsepower is created is by an increased intake volume of air into the charger housing and a larger inlet. The exhaust side is just spent gasses leaving the wheel.

 

I've read that wrapping the exhaust manifold before the turbo, the turbo, and about 3 feet of exhaust pipe exiting the turbo is all that you need to do to be effective retaining heat in the exhaust system to allow the exhaust gases to exit faster. Wrapping the exhaust any farther than that is pointless. And besides, almost every truck out there has a 90* elbow somewhere, some have two, there's just no avoiding that - every 90* bend in an exhaust pipe is equivalent to adding 13' or 15' feet of more exhaust pipe as a restriction for exhaust gases to run thru. The most efficient exhaust would be wrapped manifold, turbo, & first 3' of exhaust pipe out of the turbo then a short grass burner pipe for exiting exhaust...

 

Just like all the cars in the NHRA running turbo motors, they have a downpipe and that's it.


Plus the flames look cool

 

Yeah but stacks look better I'll probably get blasted because I'm willing to sacrifice a little economy for something I think looks cool but I don't care it's my truck..

 

I want a set of 8" straights for my truck, just don't have the money for it right now. I don't care what others think, it is my truck and I like what I like

 

I used to drive for a guy that had me in a W900 with 8" straights on a 525 cummins. The AC was broke so I always had the windows down in the summer (in Washington State) and when I would turn on the jakes, I thought I was going to lose the fillings in my teeth! Geezus it was loud, cool as all get out but way crazy loud

 

To small a exhaust will create back pressure problems though. More of a problem on cars though. One big down pipe works best put big stacks look cool.

 

But on a naturally asperaited engine, the flow is different than that of a turbocharged motor. on a N/A motor your headers will determine the amount of backpressure. You have to rememeber that on a turbo motor the charger is bolted directly to the exhaust manifold so the resistence is immediate, no matter how small the exhaust pipe is after that.